[Digestion] Digestate as fertilizer.

[Anand Karve]

Dear Jean-Luc,
on dry weight basis, green leaves have the same nutritional calorific
value as sugar. Therefore, when farmers apply green manure to crops,
they are also feeding the soil microbes. It is recommended by many
sugar factories in India to grow a green manure crop between the rows
of sugarcane, at the time of planting sugarcane, and then to plough
the green manure into the soil at two month stage of the crop.
Analysis of soils before and after this operation showed an almost
doubling of N,P and K in the soil. This increase in NPK did not come
directly from the green matter incorporated into the soil but through
the microbes, which multipled their numbers when they fed on the green
matter and took up minerals directly from the soil. We acknowledge the
fact that the top 10 to 15 cm layer of soil in a field is very
fertile, but we do not call it humus, because the organic content in
our soils is always very low. The fertility of this layer is
contributed by the fact that leaves, animal dung, and other organic
residues fall on top of the soil, where they are decomposed by aerobic
micro-organisms. As I stated above, the microbes multiply their
numbers when provided with any source of organic carbon. In the
process of multiplication, they take up the minerals directly from the
capillary water in the soil. Soil contains an infinite variety of
microbes, and those which are best adapted to that particular soil
condition multiply. If the soil is phosphate deficient, the phosphate
solubilizing bacteria would multiply. If the soil were nitrogen
deficient, the N-fixing microbes would be better able to survive than
the non-fixing ones, and if the soil were saline, the halophytic
microbes would have the upper hand over others. It is plain "survival
of the fittest". After the microbes have exhausted the food, they die
of starvation and release the organo-mineral compounds into the soil,
increasing thereby the soil fertility. The organo-mineral complexes,
such as proteins, enzymes and co-enzymes are soluble in water and they
can be readily taken up by plants. The plants don't care from which
category of microbes they get their minerals. There is no need to
apply chemical fertilizers to the soil. And there is also no need to
apply any special kinds of bacterial cultures to the soil.
Yours
A.D.Karve

On Mon, Jul 4, 2011 at 3:05 PM, Jean-Luc Sallustro
<jean-luc.sallustro at eventure-international.com> wrote:
> Dear Anand,
>
> I am really interested by this vision of sugar nutrient cycle.
> Let me say first that even if I am from Europe, (you are right on this
> point) my group is in Mauritius, and then involved with sugar cane agronomy
> (or other Poacae)
> Sure that cellulose is a kind of sugar ... but strongly polymerized, at a
> point that the only bacterial strain enabling its degradation is aerobic and
> particularly thermophilic.
> Soils macro decomposers such as colemboles or worms alternatively or
> complementary play a role within this decomposition stage of cellulose and
> hemicellulosis.
> What seems to me of utmost interest in your assessment is that sugar (I
> assume you are considering raw sugar ?) provides for direct enhancement of
> soil fertility (when bring with organic N) for the reason that this
> immediately available energy positively stresses bacterial flora (but which
> strains in particular ?) and then allows the production of mineral nutrients
> to reach the plants depending on export demands (Poacae are C4 type and
> therefore strongly dependant from photocycles and water availability).
> The way different +/- polymerized sugars reach the soil is a well known
> thing, but what's about humus role (even as thin it seems ... there is
> always an upper layer of biomass on the 0 to 15 cm depth of soils), and what
> is happening as an interaction between microbial activity in this superior
> soil level, sugar solution (rain fed context) and other N linked bacterial
> strains ?
> My hypothesis was that there is a risk of demobilisation of these endemic
> bacterial strains, maybe one can put the question like this "when stopping
> "sugar feeding" what will happen with organic N, P and K availability ?"
> All the best
> Jean-Luc
>
> Le lundi 04 juillet 2011 à 12:11 +0800, Anand Karve a écrit :
>
> Dear Jean-Luc,
> feeding sugar to the soil microbes is done by the plants themselves.
> The water of guttation of sorghum and safflower contains sugar. All
> the plants that are infested by aphids also drop sugar on the ground
> below their canopy. The leaves that fall on the ground also contain a
> type of sugar (cellulose), In the case of many trees, one finds a
> carpet of fruits underneath their canopy. The fruits contain sugars.
> Chickpea (Cicer arietinum) leaves exude organic acids, which too fall
> on the ground to feed the soil microbes. In India, in the region where
> I live, literally thousands of farmers have taken up the practice of
> applying sugar to the field. For every hectare,they use a mixture of
> 25 kg sugar, 25 kg cattle dung and 25 litres cattle urine. It is
> applied once every three months. In an earlier experiment, I got the
> soil from a non-irrigated and non-fertilized field analysed
> consecutively for 5 years and found that in spite of growing crops on
> this soil, there was no change in the soil composition over this
> period. In India, the agricultural yield is positively correlated with
> the rainfall and not with any other factors like the sale of
> fertilizers, pesticides, hybrid seed, etc. Humus is a typical topic
> raised by European agricultural scientists. Nobody talks of it in
> India, most probably because our soils do not have the humus layer
> that European soils have.
> Yours
> A.D.Karve
> On Sun, Jul 3, 2011 at 10:52 PM, Jean-Luc Sallustro
> <jean-luc.sallustro at eventure-international.com> wrote:
>> Dear A  D Karve
>>
>> For my understanding microbes have an important role in the soil at a
>> stage
>> where endemic proto nutrient are made available for them within the humic
>> clay complex.
>> This deep stage of macro nutrient (organic NPK) evolution can be depleted
>> for many reasons such as K sustainable sequestration, unavailability of
>> macro nutrient, not enough water percolation (soil solubility) etc.
>> Don't you think that one of the risks of depletion in N chain can be the
>> demobilization of upper soil decomposers due to the fact that immedialty
>> avalible nutrient are provided (sugar)
>> Regards
>> J-L Sallustro
>>
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-- 
***
Dr. A.D. Karve
President, Appropriate Rural Technology Institute (ARTI)

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